Two stage carburetion system



1957 H. A. CARLSON EIAL 2,783,032

TWO STAGE CARBURETION SYSTEM 2 Sheds-Sheet 1 Filed May 17, 1954 INVENTORS HAROLD A. CARLSON JAMES T.W. MOSELEY AT I'ORNEY Feb. 26, 1957 Filed May 17, 1954' H. A. CARLSON EI'AL TWO STAGE CARBURETION SYSTEM 2 Sheets-Sheet 2 BY JAMES T.W. MOSELEY ATTORNEY United States atent i TWO STAGE CARBURETION SYSTEM Application May 17, 1954, Serial No. 430,078

4 Claims. (Cl. 261-23) This invention relates to two-stage carburetion systems for internal combustion engines, particularly, of the automotive type and consists, more particularly, in novel means for operating the secondary throttling valve therein.

It has previously been suggested, for instance, in Kishline et 21]., Patent No. 2,193,533, that the secondary throttle valve of a two-stage carburetion system may be operated by a suction motor having a fluid connection to the primary induction conduit anterior to the throttle therein. It has been found, however, that in some cases the operating suction available at this point is insufiicient to provide for full opening of the secondary throttle valve without the use of a suction motor diaphragm and spring of impractical size so as to obtain a sufliciently low rate of spring action. This difficulty is overcome in the present invention by modulating the operating suction applied to the suction motor by means of an air bleed connected either to the motor operating suction passage or to the pressure chamber itself. The bleed, in turn, is modulated during initiation of the second stage operation of the system so as to, in effect, increase the range of suction effective upon the suction motor at such time and, thereby, produce the desired secondary throttle action with the use of a more practical suction motor and spring.

In the accompanying drawings which illustrate the invention:

Fig. 1 is a side view of a two-stage carburetor embdy-' ing the invention, portions being broken away and sectioned.

Fig. 2 is a side view showing the lower portion of the opposite side of the carburetor.

Fig. 3 is a side view similar to Fig. 2, but showing other portions broken away and sectioned.

Fig. 4 is a view similar to Fig. 3 but showing the throttle valves in partially opened positions.

The carburetor illustrated has a pair of downdraft induction conduits arranged in a unitary structure. Primary induction conduit has centrally located venturi tubes 11 and 12 forming a mixing chamber and a throttle valve 13 controlling the outlet portion thereof. Secondary induction conduit 14 has venturi tubes 15 and 16 and a throttle valve 17 controlling the outlet portion thereof. Constant level fuel bowl portions 18 and 19 are provided at opposite ends of the carburetor and fuel is supplied therefrom through metering orifice elements 20 and 21 in the bowl portions communicating with up wardly inclined main fuel passages 22 and 23 discharging, respectively, into venturi tubes 11 and 15. Idling fuel is supplied through passages 24 and 25 extending from the main fuel passages to ports 26 and 27 located adjacent and slightly posterior to the throttle valves 13 and 17 when closed. An adjusting screw 28 is provided for one of the idling ports 26. The entrance of air to primary induction conduit 10 is controlled by a choke valve 29 which is operated by an automatic choke control of any well known type located in a housing 30.

2,783,032 Patented Feb, 26, 1957 ates with an outward lug 38 on an arm 39 loosely re-- ceived about shaft 36 just inwardly of finger 35. Arm 39 is connected by a link 40 to a bell crank 41 rigid with the adjacent projecting end of secondary throttle shaft 42. The other arm of bell crank 41 is connected by a rod 43 to a diaphragm 44 clamped between suction motor housing portions 45 and 46. Housing portion 45 is formed integral with the body portion of the carburetor and is braced by ribs 47 and 48. An opening 49 in the transverse web of housing portion 45 admits rod 43 and also exposes the undersurface of diaphragm 44 to atmospheric pressure. A motor operating suction passage 50, partly in rib 47, communicates with the pressure chamber formed between diaphragm 44 and upper motor housing portion 46. Secondary throttle 17 is positively closed upon closing of the primary throttle by engagement of radial finger 35 with. lug 38.

As best shown in Figs. 3 and 4, one end of primary throttle shaft 36 is journaled in a rectangular boss 52 formed on the throttle body and this journaled portion of the throttle has a segmental valve forming groove 53. An air bleed port 54 is formed in boss 52 and communicates with slot 53 until the primary throttle valve is nearly fully opened. A passage 55 connects the shaft journal with venturi tube 12 in the primary induction conduit lib. The aforementioned suction motor operating passage 51) communicates with the shaft journal between bleed 54 and passage 55. Thus, passages and 55 combine to form the motor operating passage with modulating valve 53 and bleed 54.

Figure 2 shows an operating lever 56 secured to the opposite end of primary throttle shaft 36 and having an arm 57 with an aperture 58 for connection by suitable linkage to the accelerator pedal in the drivers compartment. Lever 56 is connected bya link 59 to the usual accelerator pump mechanism (not shown). Pivotally mounted adjacent lever 56 is a fast idle cam 60 connected by a link 61 to the choke valve. An adjusting screw 62 carried by lever 56 co-operates with cam 60 so that during cold starting and warm-up, closing of the primary throttle is limited to the so-called fast'idle position. When the engine reaches its normal operating temperature, the high portion of cam 60 is out of register with screw 62 so that a pad on throttle operating lever 57 may engage normal idle adjusting screw 63 carried by a lug 64 on the throttle body. An inward lug 57a on primary throttle operating lever 56 is positioned to engage a-radial finger 60.2 on fast idle cam 60 so as to positively open the choke valve for unloading purposes. This fast idle and unloading mechanism is conventional and is believed adequately illustrated for illustrative purposes.

In operation, when both throttle valves are closed, as in Fig. 3, valve slot 53 connects bleed 54 to suction motor operating passage 50 so that atmospheric pressure is transmitted thereby to the suction motor pressure chamber; If desired, bleed 54 may be connected to the air inlet portion of the carburetor or to the air cleaner or another zone of atmospheric pressure during first stage operation. When the primary throttle valve is opened during first stage operation to a predetermined position, say 60 degrees, as in Fig. 4, valve slot 53 begins to cover bleed port 54 and to uncover venturi suction passage 55 so as to communicate the suction in venturi 12, reduced by the air bleeding through port 54, to the suction motor. When the speed of the associated engine is sufficient, under these conditions, the secondary throttle valve will start to open to initiate second stage operation of the sys tem. During continued opening of the primary throttle valve, the uncovered portion of bleed port 54 is progressively reduced and may be finally eliminated when the primary throttle is fully opened. Conversely, venturi passage 55 is progressively opened and exposed to slot 53 and motor passage 50, during the final portion of the first stage operation so that When the primary throttle is substantially fully opened, the full etfect of venturi suction is applied to the suction motor. The etfect of this is to reduce the effective suction applied to the suction motor at the beginning of the second stage operation of the carburetion system while transmitting maximum suction to the motor when it is desired to obtain full opening movement of the secondary throttle valve.

During second stage operation, the secondary throttle valve may fluctuate in accordance with suctionconditions in the primary induction conduit to provide for the greater capacity needed at higher speeds. Upon initial closing of the primary throttle valve, radial finger 35 engages and rotates lug 38 clockwise so as to start to close the secondary throttle valve. When the primary throttle reaches the approximate position of Fig. 4, the motor operating suction passage is again exposed to air bleed 54 so that the effective suction applied to the motor is quickly reduced, thus, insuring rapid closing of the secondary throttle valve by motor spring 51.

The primary and secondary stages may be formed separately if desired and the induction conduits thereof may be duplicated. Also, the modulating bleed passage may communicate directly with the motor pressure chamber rather than through the motor operating suction passage. The exclusive use of all modifications as come within the scope of the appended claims is contemplated.

We claim:

1. A two-stage carburetion system comprising primary and secondary induction conduits having primary and secondary throttle valves, respectively therein, manual means to operate said primary valve, a spring urging said secondary valve closed, a suction motor operatively connected to said secondary valve and having a pressure chamber, a suction connection between the pressure chamber of said motor and said primary induction conduit whereby said motor is actuated and said secondary valve opened against said spring upon increases of suction in said primary conduit, and means to modulate the effective suction applied to said motor comprising an air bleed passage communicating with the pressure chamber of said motor, and valve means actuable with said primary throttle valve and controlling both said suction connection and said bleed passage for progressively cutting olf said bleed passage and opening said suction passage to said suction motor as said primary throttle valve is opened to initiate second stage operation of the system. 2. A two-stage carburetion system comprising primary and secondary induction conduits having primary and secondary throttle valves, respectively, manual means to operate said primary valve, a suction motor operatively connected to said secondary valve and having a pressure chamber, a suction connection between said pressure chamber and said primary induction conduit, an air bleed passage communicating with said pressure chamber and normally open to substantially atmospheric pressure, and means operable responsive to movement of said primary throttle. valve as it approaches its full open position to close said air bleed passage and to open said suction con nection, whereby said, motor is actuated and said second ary valve is opened.

3. A two-stage carburetion system comprising primary and secondary induction conduits having primary and secondary throttle valves, respectively, manual means to operate said primary valve, a suction motor operatively connected to said secondary valve and having a pressure chamber, a suction connection between said pressure chamber and said primary induction conduit, an air bleed passage communicating with said pressure chamber and normally open to substantially atmospheric pressure, and means operable responsive to movement of said primary throttle valve as it approaches its full open position to close said air bleed passage and to open said suction connection, whereby said motor is actuated and said secondary valve is opened, and resilient means yieldably resisting movement of said secondary valve toward its open position.

4. A two-stage carburetion system comprising primary and secondary induction conduits having primary and secondary throttle valves, respectively, manual means to operate said primary valve, a suction motor operatively connected to said secondary valve and having a pressure chamber, a suction connection between said pressure chamberand said primary induction conduit, an air bleed passage communicating with said pressure chamber and normally open to substantially atmospheric pressure, means operable responsive to movement of said primary throttle valve as it approaches its full open position to close said air bleed passage and to open said suction con nection, whereby said motor is actuated and said secondary valve is opened, resilient means yieldably resisting movement of said secondary valve toward its open position, and means operable responsive to movement of said primary valve toward its closed position to positively and simultaneously move said secondary valve from an open position towards its closed position.

Olson Mar. 9, 1943 Winkler et a1. Nov. 27, 1945 

